| Summary: | 碩士 === 國立成功大學 === 醫學工程研究所碩博士班 === 98 === Abstract
Because of improvement and development of the medical technology, the dramatic increase of aged population and associated osteoporosis has lead to increase patients with spinal trauma and related spinal disorder. In 2000, the America National Osteoporosis Foundation reported that there are over 140,000 vertebral fractures annually. The transpecicle screw system has been widely used to treat spinal disorder in the past two decades. Loosing or pullout of the pedicle screws occurs in cases of inadequate fixation strength between screw-bone interface,especially in patient with osteoporsis. However, it is a challenge to s perform for instrument on the osteoporotic spine. The purpose of study is to design and develop of bone cement anchoraged pedicle screw for osteoporotic spine. The specific aims are to: 1) design and development of bone cement anchoraged three-dimensional model of pedicle screw. 2) applying finite element method (FEM) to simulate and analyze the biomechanical characteristics of the inserted bone cement anchoraged pedicle screw and bone cement into the vertebre (including at least three vertebrae) for optimal design of the pedicle screw.
This study is divided into four stages: (1) applying computer aided engineering (CAE) to conceptual design a 3D bone cement anchoraged pedicle screw for osteoporosis, and prototype manufacture. (2) monitoring bone cement distribution patterns for pedicle screw types inserted into sawbone test block to prove the feasibility. The occupied space of different bone cement distribution is also quantitatively characterized for length, diameter, and volume by using a SolidWorks program. (3) pedicle screw with bone cement into sawbone test block of biomechanical tensile strength test conducted using MTS and divided into 12 groups. To evaluate the effect of different methods of the pedicle screw implantation on the stability of the fixation, one-way analysis of variance (ANOVA) is applied to compare the pullout strength and energy. (4) applying finite element method (FEM) to simulate and analyze the biomechanical characteristics of the inserted bone cement anchoraged pedicle screw and bone cement into the vertebra (including at least three vertebras).
The analytical results show that : (1) the bone cement anchoraged pedicle screw present a 5 % increase in tensile strength of the von mises stress compared with conventional pedicle screw and a 6 % increase in the total reaction force. The bone cement anchoraged pedicle screw a 3 % increase in bending strength of the von mises stress compared with conventional pedicle screw and a 3 % increase in the deformation. (2) A significant increase in the pullout failure strength of pedicle screws with PMMA bone cement augmentation relative to pedicle screws without bone cement augmentation is observed among each group ( P ＜ 0.05 ). (3) traditional screw and bone cement anchoraged pedicle screw using PMMA bone cement augmentation will significantly reduce the overall von mises stress of 27 to 44 percent in pedicle screw and associate augmentation bone cement into the three vertebra model.
The outcomes of this research have suggested : the higher strength of pedicle screw fixation in osteoportic spine can be obtained with the larger amount of bone cement inject, but this may increase the risk of cement leakage. Future works suggest that bone cement anchoraged pedicle screw for cadver biomechanical and animal experiments for clinical treatment of osteoporosis an an alternative to spinal fracture to provide more complete information.
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